Since I’m going to drive a hot wire for my foam cutter, I thought it might be quite neat if I could control the hot wire via smoothie.
It is probably not very feasible to temperature control the wire reliably. (Will see I will do some tests with that. But I don’t think it’s viable)
But temperature control doesn’t need to be super precise. Ideally I could just set the current for the wire. That is why I got quite excited about the currentcontrol feature. But it is not quite clear to me what current it controls. The G-Code M907 accepts values for X Y Z E. I suppose those are for the stepper channels.
I would of course need that at one of the big mosfet heater outputs.
Alternatively, is there perhaps a PWM mode for the big mosfets? I see no gcodes for that or any other references.
Imported from wikidot
I should really read the docu before I post. I found the switch module. And it supports PWM.
That is that. Probly also makes more sense than current regulating. Since that would probably be a linear regulator, and that would get rather hot.
I think that you have put a good question.
Simple PWM without feedback it’s not that usefull.
a simple OPAmp would help to do conversion from Thermistor to constant current.
I will think about how to implement it.
I did some research too. Nobody seems o do any temperature regulation on hotwire cutters.
They all find the right cutting speed and power on the wire setings by experimantation and just leave it. Or establish a few tested profiles of PWM and cutting speed for various demands.
This seems to work fine.
I guess it could be quite dificult to actually meassure the wire heat. Especially since the wire in air temperature is probably not even the most relevant value.
To take his up one notch I could consider a variant of the laser control module. In one step you heat up the wire to nominal ‘in air’ temperaure. (Like ramping up spindle speed)
And then when actual cutting is done, you can ad a few ticks more juice to the wire to compensate cooling as it eats through foam. 
But in any case. Fixed value PWM seems to be what everyone else does. So it’s good enough for me.